Question 1202418
The freight train headed south at 9 a.m. and the express train headed north from the same station at noon. At 3 p.m., the trains were 420 miles apart. What was the speed of each if the speed of the express train was 20 mph greater than the speed of the freight train?

Let speed of freight train be x mph
speed of express train = (x+20 ) mph
after 6 hours they were 420 miles away from each other

Distance = speed * time 

They are movig away from each other. 

6x+6(x+20)=420

6x+6x+120=420
12x =300

speed of freight train = 25 mph

speed of  express train = 25+20 =45 mph